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Sandvik Coromant has supplied the GC4225 indexable insert grade to Metax to help the company achieve more efficient machining operations.

Metax is a manufacturer and supplier of rotating mechanical seals, rotary joints, couplings and basic seals, primarily for the chemical and petrochemical industries.

Medical technology equipment, particularly for orthopaedic applications, is also produced.

Product designs not only exploit conventional materials such as non-ferrous metals, stainless steels and low-carbon steels, but also heat-resistant super alloys such as Hastelloy, Inconel and Stellite, which involve risks as well as opportunities.

Stellites are cobalt-chromium alloys that offer thermal and chemical resistance at temperatures in excess of 800C.

In addition, their variable hard material content can be used to obtain specific wear resistance.

Wherever wear occurs in combination with high temperatures and/or aggressive media, the use of Stellite offers advantages.

It is frequently used as a coating or lining over less-tough base materials.

However, machining Stellites is not without its problems, particularly as they frequently demonstrate hardness values up to 55 HRc.

Consequently, Stellites are typically ground or machined using cubic boron nitride (CBN), the second hardest material after diamond.

Its advantage is that, unlike diamond, CBN does not impart carbon to steel at elevated temperatures.

At Metax, Stellite is used to line and coat a number of the company’s products, including bearing bushes, which are made from austenitic stainless steel 1.4571.

Metax applies the Stellite internally and to the end faces of the bearing bushes before finish-turning.

Machining the workpiece presented the team, led by Heiko Konig, head of manufacturing at Metax, with a number of problems.

Essentially there are two different materials to be cut, each requiring a different chip depth and machining method.

The transition zone where the two layers meet is another challenge.

With Stellites, the transition zone is quite literally the crunch point: while CBN is very good at cutting hard Stellite, it causes problems with softer base materials because it breaks out during cutting.

Consequently, in most practical instances the soft base is machined conventionally as far as the applied Stellite layer, which is then cut using CBN.

The problematic transition zone is more or less ‘incidentally’ machined.

Overall, this process is both time consuming and expensive, and using its existing indexable insert solution Metax had a tool life of only two workpieces.

To help combat the situation, Konig contacted Rainer Lich, a member of the sales team at Sandvik Coromant distributor R Alfred Zimmerman.

GC4225, a grade in the new indexable insert generation from Sandvik Coromant that Lich and Konig had been using in production since its market introduction in 2005, had been particularly successful.

‘GC4225 has become an all-round grade for us,’ said Konig.

‘Our production is predominantly in small batch sizes and frequently single parts.

‘In the past, we always had to change inserts even after shallow cuts.

‘With GC4225 from Sandvik Coromant, we have a carbide grade that we can use to cut not only stainless steel but also more exotic materials such as Hastelloy or Inconel,’ he added.

The new indexable inserts have another advantage, according to Lich.

‘The change means that we can reduce the large number of carbide grades in use, which would otherwise be tying up capital and warehouse capacity,’ he said.

Encouraged by the outcome of using GC4225, the two men decided to try the insert for machining Stellite.

GC4225 allowed the entire end face to be turned in a single pass – not just the soft and the hard material, but also the problematic transition zone.

The insert is applied using 15m/min surface speed, a feed rate of 0.1mm/rev and a cutting depth of 0.5mm, cooled with emulsion.

The fact that the insert no longer required replacement resulted in a more efficient and economic working operation.

‘The tool life was increased by 500 per cent to 10 workpieces with the same cutting data,’ said Konig.

Sandvik Coromant

Part of global industrial engineering group Sandvik, Sandvik Coromant is at the forefront of manufacturing tools, machining solutions and knowledge that drive industry standards and innovations demanded by the metalworking industry now and into the next industrial era.

Part of global industrial engineering group Sandvik, Sandvik Coromant is at the forefront of manufacturing tools, machining solutions and knowledge that drive industry standards and innovations demanded by the metalworking industry now and into the next industrial era.

Educational support, extensive R&D investment and strong customer partnerships ensure the development of machining technologies that change, lead and drive the future of manufacturing. Sandvik Coromant owns over 3100 patents worldwide, employs over 8,500 staff, and is represented in 150 countries.

For more information visit www.sandvik.coromant.com or join the conversation on social media.

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